lime

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Lime construction has existed for centuries, all over the world. We are fortunate to experience and draw from thousands of years of traditional building knowledge in our country and regard it as a huge resource. Thermal comfort, cost of construction and durability of the structure define our core objective.
Re- exploration of lime in masonry construction and plasters for building is a work in progress. Documentation of traditional techniques, in western India, testing of materials over a period of time and use of I.S codes for lime construction guide our current work. A deeper understanding of such materials, their chemistry and practices is essential. We believe that sharing such knowledge will lead to a better awareness about the choices we make as professionals.

a) Rasi Gud (liquid jaggery): Is molasses obtained from sugar factories, also called ‘rasi no gud’ in Gujarati. Should be fluid, dark brown in colour. Dilution 15 lit Rasi no Gud + 200 lit water. To be stored in a 200 lit drum with a lid.
b) Chuna(lime) : Lime, slaked in a slaking tank and allowed to settle. Periodically mixed and always stored under 3 inches of water.

c) Lapti- A wash of ‘lime –RasiGud/molasses diluted’ mix is prepared for use before the first plaster coat. The proportions in this case are10 liters of diluted molasses and 1 tagara kali chuna. (hydrated lime)

Note: Lime and molasses when mixed to form lapti should turn to a bright yellowish / ochre colour.This wash gives the necessary bonding for the wall when the first rough coat is applied.
d) Methi (fenugreek) /Guggal (Commiphora muku): vendor: LVG Ambawadi Ahmedabad or other reliable source.
*Boil Methi & Guggal in desired proportions: varies for summer/winter use.
*Summer use 20 liters water+ 200gms methi+100gms guggal
*Winter use 20 liters water+200gms methi+200gms guggal
Note: The solution may have a foul smell after a few days but can be stored and used as per proportions below. This mix is for use in plasters only.
Mixing in about 2 lit of water, boil and dissolve to obtain aresinous solution. Mix this solution in 20-lit water to get a20-lit solution of methi and guggal.
e) Lime forMortar : Hydrated lime slurry w/1:2:9 gauged mortar as per structural

a: Mortar mix proportions in lime mixer/grinder and process: for masonry work

Proportions lime: 6 parts
Sand: 8 parts
Surkhi: 7 parts: (made from brick bats crushed in grinder)
Lapti: 1 liter per ‘Ghani’ (Mortar mixer container as 1unit)
Grind the above in lime mortar mixer for 20 minutes or until correct consistency is achieved. Mortar consistency must be such that it forms a sticky lump. This must stick when slapped against wall.

b: Testing Conduct cube tests to ensure that the strength achieved is correct. Test for 7/14/28 days and compare results as per I.S specification for structural approval.

c: Process – Masonry work

Step 1 Wet and soak bricks thoroughly prior to start of work.
Spread mortar evenly across the brick. Allow excess mortar to press out of masonry unit. This excess mortar should be raked out with a trowel to create a good seat for the first coat of plaster. Vertical joints to be packed with mortar and checked each time. No voids shall be left between brick joints.

Step 2 Curing: The masonry wall is to be covered with a wet jute cloth immediately to prevent quick drying.
Curing by spraying the jute 3 times a day in summer and twice a day in winter is important.
Curing must be done until initial strength for at least seven days is achieved.
Top of wall to be protected with a layer of mortar during rainy conditions.

Mix should be a bit coarse. Particles of brickbat not to be ground too fine for first coat.

Step 1 Throw plaster mix with trowel onto wet wall. Use wood planer (2’ wooden muster) to spread where needed and leave coarse. Ensure even thickness of 12mm (usual normal first coat application practice to be followed as in cement plasters) surface will appear coarse with spikes and undulations. Surface should be in level but not flattened. Allow to set. If a second surface preparation coat is needed to level and coat the wall surface, the same shall be done after 4 days. Each coat must not be more than 6mm thickness at any time.

Step 2 Curing : The setting time is recommended to be 24 hours after which curing should begin (water to be sprayed thrice a day in summer Morning/noon/evening), twice in winter (morning/evening) over a jute cover on plaster, not directly). Use a small fine shower nozzle.
The curing should be carried out for a minimum period of 3 days / or until adequate strength is seen in the surface.
** (Simple test for strength- Try to score lines onto the surface with the edge of a trowel. The surface must be hard. This must be done before the second coat is started)

Step 3 2nd plaster coat The application of the second coat should not be earlier than 4 days after the first coat is applied.

Note: This is the final leveling coat. Line & level to be checked and finalized in this coat including rounding of edges.
Make small diagonal strokes across the surface using the wood planer to roughen surface lightly to prepare base for the final coat.

Step 4 Curing : The setting time is recommended to be 24 hours after which curing should begin (water to be sprayed thrice a day in summer, twice in winter over a jute cover on plaster, not directly) Last curing of day to be done in the evening.
The curing should be carried out for a minimum period of 4 days. The application of the final coat should not be earlier than 4 days after the first coat is applied. The final coat can be done even after a month, but not without proper wetting of the wall surface.